The present study was conducted to investigate the acute toxicity of plant sterol ester by a single oral dose in Sprague-Dawley rats. Ten males and 10 females aged 5 weeks were randomly assigned to two groups of 5 rats each and were administered by gavage at dose level of 0 or 20 ml/kg body weight. Parameters measured during the 14-day observation period were mortality, clinical signs, body weight changes, and gross findings. No mortality was observed in the present study. Treatment-related clinical signs, such as pasty stool and diarrhea, were observed on the day of treatment and these signs resulted in soiled fur on day 1 after the treatment. However, no clinical signs were observed on days 2-14 after the treatment. There was no significant difference in body weight changes between the control and treatment groups. At necropsy on day 14 after the treatment, no treatment-related gross findings were observed in the treatment group. Based on these results, it was concluded that a single oral dose of plant sterol ester induced pasty stool and diarrhea in Sprague-Dawley rats at dose level of 20 ml/kg and that the lethal doses were considered to be over 20 ml/kg for both sexes.